Single vibronic level emission spectroscopy of the system of bromochlorocarbene

Multireference Configuration Interaction Study of Bromocarbenes

“…For the ground singlet state, experimental results are available for all of the compounds except CIBr. [33][34][35][36][37][38] For CClBr and CBr 2 , the harmonic vibrational frequencies of the ground singlet state computed in this work are in excellent agreement with experimental harmonic values, 37,38 exhibiting differences of less than 35 cm -1 . For CHBr, the computed value of the bending mode ω 2 is within 1 cm -1 of the experimental anharmonic value (the anharmonicity is expected to be low in this case), 33,34 while the calculated harmonic stretching modes ω 1 and ω 3 differ from the anharmonic experimental frequencies 33,35 by about 40-50 cm -1 ; however, these differences correspond to less than 4% for ω 1 and less than 2% for ω 3 .…”

“… a Experimental results are listed in brackets. In the table, ω 1 corresponds to the CXBr low-frequency stretch (or CBr 2 symmetric stretch), ω 2 corresponds to the bend, and ω 3 corresponds to the CXBr high-frequency stretch (or CBr 2 antisymmetric stretch). b Reference . c Reference . d Reference . e Reference . f Reference . g Reference . h Reference . i Reference . j Reference . k Reference . l Reference . m Reference . …”

“…The calculated harmonic vibrational frequencies of the bromocarbenes obtained at the MRCI/cc-pVTZ level are presented in Table 3 along with available experimental results. 12,26,31,[33][34][35][36][37][38][39][40][41] In the results presented, the harmonic frequency ω 1 corresponds to the CXBr low-frequency stretch (or CBr 2 symmetric stretch), ω 2 corresponds to the bend, and ω 3 corresponds to the CXBr high-frequency stretch (or CBr 2 antisymmetric stretch). In some cases, as will be elaborated further, the reported experimental frequencies include anharmonic effects while the calculated results are harmonic; therefore, in those cases the calculated harmonic frequencies are generally expected to be higher by about ∼5-10% compared to the experimental anharmonic frequencies.…”

Fluorescence Excitation and Emission Spectroscopy of the X̃1A′ → Ã1A′′ System of CHI and CDI

“…Over the past decade, several experimental groups, including our own, initiated detailed spectroscopic studies of the monohalocarbenes. [48][49][50][51][52][53][54][55][58][59][60][61][62][63][64][65][66][68][69][70] Despite this large body of work, only last year was the spectrum of an iodocarbene, :CHI, reported by us after an extensive effort. 66 The vibronic assignments in the electronic spectrum were unclear, as only bands lying quite far above the origin were measured, yet this work established a singlet multiplicity for the ground state and gave a lower limit on the singlet-triplet gap of 3.76 kcal mol -1 , using a deperturbation analysis of SVL emission spectra.…”

“…As the smallest carbenes with singlet ground states, the monohalocarbenes (:CXY; X = H, F, Cl, Br, I; Y = F, Cl, Br, I) have served as important prototypes for understanding the spectroscopy of carbenes, and benchmarks for theoretical predictions of carbene singlet−triplet gaps. Over the past three decades many theoretical studies have appeared on the topic, using a variety of ab initio methods. − Experimental studies of the singlet−triplet gap, while less numerous, have also exploited a variety of techniques, including negative ion photoelectron spectroscopy (PES), − emission spectroscopy, − and stimulated emission pumping (SEP) spectroscopy. − The SEP method was first demonstrated in the laboratory of Robert W. Field in the late 1970s, − and it is a pleasure for us to contribute to this volume in his honor.…”